1. Field of the Invention
The present invention relates to a lens-fitted photo film unit with a mechanism to prevent improper replacement of a photo film cartridge. Moreover, the present invention relates to a method for reusing a lens-fitted photo film unit with such mechanism.
2. Description Related to the Prior Art
A lens-fitted photo film unit, in which an unexposed photo filmstrip is preloaded and a simple photographic mechanism is provided, is available for sale in the market. After use, the lens-fitted photo film unit is collected by a manufacturer and disassembled into components for reuse.
Recently, some lens-fitted photo film units in the market are manufactured by loading an unexposed photo film cartridge improperly into a used film unit. As a result of improper examination or lack of repair, such improper lens-fitted photo film unit causes more trouble than a properly fitted reused photo film unit. Since this kind of trouble causes lens-fitted photo film units to be less reliable, a conventional lens-fitted photo film unit is incorporated mechanisms to prevent improper reuse.
For instance, it is possible to prevent improper reuse by fixing a rear cover, removed in film replacement, to a main body firmly by ultrasonic welding. Moreover, JPA 7-120883 discloses a lens-fitted photo film unit in which an anti-reverse claw is broken when the lens-fitted photo film unit is disassembled. The anti-reverse claw is in mesh from behind with an engaging claw that is formed with the rear cover. When the rear cover is forcibly removed, the engaging claw pulls the anti-reverse claw causing it to be deformed or broken.
The above-mentioned lens-fitted photo film unit, however, has a disadvantage in that the film unit is easily disassembled by cutting the welded portion with an ultrasonic cutter or the like. Moreover, the mechanism disclosed in JPA 7-120883 is not effective to prevent the improper cartridge replacement when the claws are not engaged firmly. In these cases, it is possible to prevent improper cartridge replacement effectively by having strict size management. Since the strict size management causes increase in manufacturing cost, it is not preferable for low-price lens-fitted photo film unit.
An object of the present invention is to provide a lens-fitted photo film unit with a mechanism to prevent improper cartridge replacement effectively at a low price.
Another object of the present invention is to provide a method for reusing the lens-fitted photo film unit with such mechanism.
To achieve the above objects, the lens-fitted photo film unit of the present invention includes an anti-reverse claw integrated with the base portion, and a welded portion integrated with said anti-reverse claw. The anti-reverse claw being is engaged with the winding dial to prevent the reverse rotation of the winding dial. The welded portion is welded to the rear cover, so that the anti-reverse claw is broken when the rear cover is forcibly separated from the base portion.
In a preferred embodiment, the welded portion has two welded pieces protruded rearward of the rear cover through corresponding openings in the rear cover separated by a separation plate. The welded pieces are welded to the rear cover together with the separation plate. The opening of the rear cover is surrounded by a recess formed on a rear surface of the rear cover, so that the welded pieces are melted and spread in the recess.
In a preferred embodiment, second welded portion is provided on a light-shielding rib that is integrated with the rear side of the base portion. The second welded portion projects through a second opening formed in the rear cover, and welded to the rear cover to fix the light-shielding rib firmly to the base portion.
The lens-fitted photo film unit of the present invention is reused by welding a new anti-reverse claw to said lens-fitted photo film unit, so that the new anti-reverse claw engages the winding dial to prevent the reverse rotation of the winding dial. After separation of the rear cover from the base portion, the anti-reverse claw is broken and stuck on the rear cover. The anti-reverse claw on the rear cover is removed and the rear cover is smoothed. After the jointed surface of the base portion is smoothed, a new anti-reverse claw is weld to the base portion and the rear cover.
The broken anti-reverse claw may be reused by correcting its shape by inserting a support member. After the shape of the claw is corrected, the rear cover is assembled to the base portion so that the corrected anti-reverse claw is engaged with the winding dial to prevent reverse rotation.